1. Field of the Invention
The present invention relates to an ophthalmic apparatus which performs examination or measurement of an examinee's eye.
2. Description of Related Art
For an ophthalmic apparatus which performs alignment of an ophthalmic examination unit with respect to an examinee's eye and performs examination of the eye, there is known an ophthalmic apparatus comprising an alignment mechanism which is provided in order to mechanically perform horizontal movement of a mobile base on which an ophthalmic examination unit is mounted with respect to a fixed main base. In addition, there is known an ophthalmic apparatus arranged to perform automatic precise alignment after manual rough alignment by comprising a driving mechanism capable of moving an ophthalmic examination unit independently in a back/forth direction, aright/left direction and an up/down direction with respect to a mobile base on which the ophthalmic examination unit is mounted (see Japanese Patent Application Unexamined Publication No. Hei08-98808). In the apparatus having such a configuration, a movable range of the driving mechanism extends only for 5 mm both in the back direction and the forth direction and both in the right direction and the left direction from a reference position (for 16 mm both in the up direction and the down direction).
In recent years, there is known an apparatus in which a movable range of a driving mechanism arranged to move an ophthalmic examination unit with respect to examinee's eyes is established to be more than a pupillary distance between the eyes for the purpose of total automation of alignment including rough alignment. In this case, the alignment of the ophthalmic examination unit with respect to each eye is automatically performed in sequence (see Japanese Patent Application Unexamined Publication No. Hei10-216089).
However, even in the case of the alignment including the rough alignment in total automation, automatic measurement of each eye cannot be made for every type of examinee. For example, if the eye involuntarily moves very rapidly, the movement of the ophthalmic examination unit by the driving mechanism sometimes cannot track the movement of the eye. In preparation for such a case that an examinee has an eye on which the automatic alignment is difficult to be performed, the above-described apparatus is equipped with an electric control member (e.g., an electric joystick, a trackball) which is operated by an examiner. The driving mechanism is driven and controlled in accordance with an amount and a direction of the operation of the control member, and thereby alignment of the ophthalmic examination unit with respect to the eye can be performed manually. However, the manual alignment using the electric control member is difficult in the operation of the control member, which could take time and trouble to perform alignment tasks.